A North Korean refugee was able to jump over the 3-meter fence along the inter-Korean border to the South without triggering the alarm because screws were loose on the fence’s sensors, South Korea’s Joint Chiefs of Staff said Thursday.

The military revealed the initial finding of its internal investigation into the event early this month, in which a former gymnast in his 20s crossed the border on foot.

Sensors on the border fences along the general outposts, south of the demarcation line separating the two Koreas, should alert guards when anything of certain weight, such as people or animals, touches them. But loose screws disabled the sensors, the military said, blaming the glitch on extreme weather conditions.

“It wouldn’t be right to say that the system has had that flaw from the very beginning, when we put it out there. But now that we have identified one, we intend to check every one of them,” a senior military officer said, adding improvements on the system were underway as well.

Installed in 2015, the sensor system had never been inspected until the recent probe. It was never part of the routine inspections by front-line units, the military said.

But the military insisted the malfunctioning sensors did not delay their capturing of the North Korean man, as surveillance cameras picked him up right away. It took 14 hours for the military to bring him into custody, though, and the military was criticized for its belated response.

The military disagreed that it was an operation gone bad, but left room for the concerned unit to handle the matter as it sees fit.

By Choi Si-young (siyoungchoi@heraldcorp.com)